From my personal experience with intermittent fasting, I noticed that after about 24 hours without food, my body truly shifts gears. Initially, it relies on stored glycogen in the liver to maintain blood sugar levels, but as these reserves diminish, the body begins producing glucose internally through gluconeogenesis. This process uses amino acids, lactate, and glycerol from fat breakdown, which helps keep blood glucose stable and supports vital organs like the brain. An interesting change I felt was increased mental clarity and stable energy, even though my glucose levels were slightly lower than normal eating levels. This aligns with how ketone levels rise during early ketosis, providing the brain with an alternative fuel source and reducing hunger. It's key to understand that a stable glucose level in the range of 65-85 mg/dL (3.6-4.7 mmol/L) is normal and indicates good metabolic flexibility. However, I learned the importance of listening to my body during fasting. If glucose drops below 60 mg/dL (<3.3 mmol/L) and symptoms like dizziness, shaking, or confusion appear, it could indicate hypoglycemia, requiring caution or medical advice. Factors such as pre-fast diet, insulin sensitivity, body fat percentage, activity level, and how adapted one is to fasting or ketosis deeply influence these results. Overall, fasting can be a powerful tool to improve metabolic health by encouraging the body to shift from sugar-burning to fat-burning, but it should be done mindfully, respecting your individual response and needs.